2018 Mac mini HDMI issues: Color, passwords (Sonoma/Sequoia

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Level 1

4 points

2018 Mac mini HDMI issues: Color, passwords (Sonoma/Sequoia

2018 mac mini os sonoma & sequoia bug report

if monitor is connected via hdmi port..

color rendering is not optimal, really lousy in sonoma

Sequoia suffers pointless, repetitive password dialogs appear at launch of disk utility app/ startup disk control panel, etc.

These issues disappear if monitor is connected via usb c port (in my case to the monitor's display port... don't have a usb c to hdmi cable to test this time)

os ventura is not impacted

Mac mini, macOS 15.7

Posted on Jul 15, 2026 1:47 PM

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Answer 1

den.thed

Level 10

95,906 points

Jul 15, 2026 4:04 PM in response to onetriadrr

What make and model number is the HDMI display...?

The later macOS versions are cable picky when it comes to cable length and quality.

I would test a shot 3.3' 8K certified high speed 48Gbps 2.1 HDMI cable in the Mac mini's HDMI port.

for example: > https://www.amazon.com/8K-HDMI-Cable-Highwings-Braided/dp/B08NX5CZTF/ref=sr_1_3?

Or optionally a USB-C to HDMI cable in one of the Mac mini's TB/USB-C ports.

for example: > https://www.amazon.com/dp/B07RXS39D3/ref=sspa_dk_detail_0?

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Answer 2

Kurt Lang

Level 9

71,507 points

Jul 15, 2026 2:09 PM in response to onetriadrr

The USB-C ports (Thunderbolt 3) are what you should be using. HDMI is not meant to used a computer monitor connection, regardless if your monitor has an HDMI port. It's meant to be used as a TV connection (YCbCr color), as opposed to an RGB color signal.

HDMI is useful if you do video editing and want to use a TV's HDMI connection as an inexpensive reference monitor.

Not that it doesn't work at all. The more expensive the monitor, the more likely HDMI will work well enough. But I mean high end monitors, like EIZO. Otherwise, HDMI should be avoided.

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Answer 3

Kurt Lang

Level 9

71,507 points

Jul 15, 2026 5:41 PM in response to onetriadrr

These issues disappear if monitor is connected via usb c port (in my case to the monitor's display port…

Then I have to wonder why you're doing anything else. Seriously, forget HDMI. Use the USB-C to DisplayPort cable you apparently already have and you're done.

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Answer 4

onetriadrr Author

Level 1

4 points

Jul 16, 2026 6:36 AM in response to onetriadrr

Looks like i'll be eating crow.

Because it appears i may have resolved the pointless password request dialog issue in os sequoia on this 2018 intel mac mini without noticing.

It a bum standard software update from 15.7.2 to 15.7.3 is likely at fault because that is when that issue first appeared.

So i thoroughly cleaned os data removing items that uninstallers left behind, then populated new apfs volumes with cleaned os data using CCC.

Then installed of latest versions sonoma & sequoia to those new apfs volumes using bootable usb install media.

Meanwhile i'm doing the same on 2 other intel minis, bouncing from machine to machine and getting sidetracked by the color rendition issue.

My apologies for the noise.

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Answer 5

onetriadrr Author

Level 1

4 points

Jul 15, 2026 4:23 PM in response to den.thed

trust me... the cable is not the issue

both monitors are samsung s22e450's purchase at same time

and the monitor is not the issue.

os ventura and every other native legacy os is not affected.

Bugs in the os, beginning in first 2026 sequoia update.

I'm not sure of the first 2026 sonoma update when color rendering went wrong.

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Answer 6

den.thed

Level 10

95,906 points

Jul 15, 2026 5:12 PM in response to onetriadrr

Forget about the cables that I suggested above, those are for connecting up-scale HDMI displays.

Those S22E450 monitors only have VGA and DVI inputs. (no HDMI input)

The S22E450D model also support DisplayPort input.

The 2018 Mac mini can easily support one of those monitors on the HDMI port using an HDMI to DVI adapter and one on the TB/USB-C ports using a USB-C to DVI adapter. Plus it can also support both of those monitors on the 2018 Mac mini's TB/USB-C ports.

see "Video Support" at > Mac mini (2018) - Technical Specifications - Apple Support

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Answer 7

onetriadrr Author

Level 1

4 points

Jul 15, 2026 5:21 PM in response to den.thed

i use a hdmi adapter for the dvi monitor port

And i use both monitors when using my m1 mini.. the m1 hdmi video out to monitor hdmi to dvi adaper

color rendering is not and has never been an issue with every other legacy native os... i have every one on external bootable backup disks.

but still missing the point... the resolution of pointless password dialogs in sequoia using usb c video out

that is the the hint where the bugs are in sonoma & sequoia

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Answer 8

onetriadrr Author

Level 1

4 points

Jul 15, 2026 6:01 PM in response to den.thed

The issue i've been chasing is those annoying pointless password dialogs in sequoia.

Like when simply launching diskutility app, or startup disk control panel... and other.

And no, i do not now nor have i ever used filevault.

Furthermore, i use that same hdmi cable to switch to a third mini at my work station.

Never an issue... until 2026 updates of sonoma & sequoia on this 2018 mac mini.

So, if switching to usb c video out and rebooting sequoia fixes the pointless password issue as well as color rendering.

And, given everything i've stated so far...

What does that suggest to you?

My first mac was a brand new se30 with a 10 MB hard disk and came with an alpha version of Aldus PageMaker...

Ive been at this for while.

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Answer 9

onetriadrr Author

Level 1

4 points

Jul 16, 2026 9:12 AM in response to onetriadrr

Not eating crow after all.

So long as there is only 1 bootable partition on the internal ssd...

Pointless "diskutility wants to make changes" password dialog doesn't appear when diskutility app is launched, but appears when another app which performs some disk activity, like CCC, is launched/being modified... and diskutility is still active.

If there is more that 1 bootable partition....

Launching diskutility app throws that same password dialog recursing for the count of bootable partitions -1.

Curiously, when i quit diskutility app, the password dialog remains on screen.

And when i cancel that dialog and if there are, for instance, 3 bootable partitions, another password dialog appears.

I can send a screen grab that shows that diskutility is not running by the absence of the "active dot" next to it's dock icon. And yet, the diskutility password dialog persists on screen. And which might have appear only after diskutility has been quit.

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Answer 10

Jul 16, 2026 1:37 PM in response to onetriadrr

onetriadrr wrote:

Not eating crow after all.

So long as there is only 1 bootable partition on the internal ssd...

Pointless "diskutility wants to make changes" password dialog doesn't appear when diskutility app is launched, but appears when another app which performs some disk activity, like CCC, is launched/being modified... and diskutility is still active.

I've only ever seen Disk Utility ask for authentication a few times when Disk Utility is first launched. Earlier this year I performed some experiments and found the only time this occurred was when an external drive had a bootable macOS installation on it. Filevault or an encrypted APFS volume did not trigger the issue. See my other post here:

Disk Utility keeps asking for a password … --- Experiment by @HWTech - Apple Community

Curiously, when i quit diskutility app, the password dialog remains on screen.

And when i cancel that dialog and if there are, for instance, 3 bootable partitions, another password dialog appears.

I can send a screen grab that shows that diskutility is not running by the absence of the "active dot" next to it's dock icon. And yet, the diskutility password dialog persists on screen. And which might have appear only after diskutility has been quit.

Yes, Apple's pop-up dialogs boxes can be very irritating and behave in very unusual ways including disappearing completely from view if another window accidentally covers it. They've been that way for years.

You can provide Apple with product feedback for both issues:

Feedback - macOS - Apple

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Answer 11

onetriadrr Author

Level 1

4 points

Jul 16, 2026 3:05 PM in response to HWTech

I have never used filevault.

These bogus password request dialogs are not limited to diskutility

Launching startup disk control panel pops its own 'wants to make changes' dialog.

Seems any app that performs some disk related activity are similarly plagued, including CCC after dragging a disk to CCC's source or destination pane.

Those dialogs are supposed to be modal aren't they? And therefore, not allow you to quit the app without dismissing the dialog first.

I'm convinced those dialogs are orphaned as soon as they appear...

which would allow those dialogs to disappear behind some other window... which i have also seen.

I'm a retired freelance graphic designer, primarily for high-end print. I started using Macs in my work before there was a RGB capable Mac and 10 MB internal SCSII disk drives were standard.

In all those years i've never been so disappointed in Apple as i am now with os Sequoia on this 2018 intel mac mini... while sequoia and tahoe behave perfectly on my m1 mini.

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Answer 12

Jul 16, 2026 6:20 PM in response to onetriadrr

onetriadrr wrote:

I have never used filevault.

These bogus password request dialogs are not limited to diskutility

Launching startup disk control panel pops its own 'wants to make changes' dialog.

Actually you should double check the "Privacy & Security" System Settings. We've seen cases where macOS 26.x Tahoe have automatically enabled Filevault without user intervention. While you are using Sonoma & Sequoia, it is possible that same thing may have occurred.

Seems any app that performs some disk related activity are similarly plagued, including CCC after dragging a disk to CCC's source or destination pane.

That is normal for CCC in order to access areas where you may not have the necessary permissions.

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